1. Field of the Invention
The present invention relates to a triode field emission display using carbon nanotubes having an excellent electron emission characteristic.
2. Description of the Related Art
In a conventional field emission display (FED), when a strong electric field is applied through gates to a Spindt""s field emitter array (FEA), which is formed of a metal such molybdenum (Mo) or a semiconductor material such as silicon (Si), that is, to microtips arranged at regular intervals, electrons are emitted from the microtips. The emitted electrons are accelerated toward anodes, to which voltage (for example, several hundred to several thousand volts) is applied, and collide with phosphors with which the anodes are coated, thereby emitting light. Because the work function of a metal or a semiconductor material used for the microtips of a conventional FED is large, the gate voltage for electron emission must be very high. Residual gas particles in vacuum collide with electrons and are thus ionized. Because the microtips are bombarded with these gas ions, the microtips as an electron emission source may break. Moreover, since particles are separated from the phosphors colliding with electrons and pollute the microtips, the performance of the electron emission source may be deteriorated. These problems may reduce the performance and life of the FEA. To overcome these problems, instead of a metal or a semiconductor material, carbon nanotubes having a low electron emission voltage and an excellent chemical stability is used for microtips. In this case, the performance and life of the FEA can be improved.
Arc discharge and laser ablation is widely used in deposition of carbon nanotubes, but these methods are not suitable for mass production of carbon nanotubes at a low cost, and structure control is difficult in these methods. To overcome these problems, vapor deposition has been developed. Representative vapor deposition methods include thermal chemical vapor deposition (CVD) (Appl. Phys. Lett. 67, 2477, 1995), MPECVD (Appl. Phys. Lett. 72, 3437, 1998) and ion beam irradiation (Appl. Phys. Lett. 69, 4174, 1996).
While the electron emission electrical field of a diamond film, which has been highlighted as a material of an electron emission source, is about 10 V/xcexcm, carbon nanotubes have a characteristic in which electrons are easily emitted even at an electrical field of 1 V/xcexcm or less. Accordingly, carbon nanotubes have been touted as the next generation material of an electron emission source.
FIG. 1 is a schematic sectional view illustrating the structure of a conventional FED using carbon nanotubes. As shown in FIG. 1, the conventional FED using carbon nanotubes includes a front substrate 1 and a rear substrate 6 which face each other, an anode 2 and a cathode 5 which are formed on the surfaces of the two substrates 1 and 6 facing each other, respectively, phosphor 3 with which the anode 2 is coated, and carbon nanotubes 4 with which the cathode 5 is coated, thereby having a diode structure. A power supply 7 is applied between the anode 2 and the cathode 5.
It is crucial to deposit carbon nanotubes on a wide area at a low cost using a method capable of controlling the carbon nanotubes in manufacturing FEDs using carbon nanotubes. It is considered that vapor deposition should be used to achieve the above purpose. Similarly to arc discharge or laser ablation, vapor deposition uses a transition metal such as nickel (Ni) or iron (Fe) or silicide such as CoSi2 as a catalyzer. Carbon nanotubes are not deposited on a structure of a predetermined pattern but have still been deposited randomly as in a diode structure. The diode structure can easily be manufactured by vapor deposition because a layer such as an insulating layer or a gate shown in a triode structure is not necessary. However, it is difficult to control emitted electrons in a simple diode structure. This disturbs the smooth performance of a display.
A field emitter using controlled carbon nanotubes is disclosed in U.S. Pat. No. 5,773,834. In this patent, a field emitter is formed in a triode structure using a grid of a net shape as gate electrodes so that emitted electrons can be easily controlled. However, the structure of the field emitter is not simple enough to be easily manufactured by vapor deposition like a diode structure.
To solve the above problem, an object of the present invention is to provide a triode field emission display (FED) using carbon nanotubes, which has a simple triode structure similar to a diode structure in which control of emitted electrons is easy, thereby allowing deposition of carbon nanotubes on a wide area at a low cost.
To achieve the above object, the present invention provides a triode FED using carbon nanotubes, which includes front and rear substrates disposed to face each other and separated by a predetermined distance, a cathode formed on the rear substrate, carbon nanotubes formed on the cathode, an anode formed on the front substrate, phosphor formed on the anode, and an extraction electrode formed on the front substrate on which the anode is formed, the extraction electrode being separated from the anode by a predetermined distance.
In another aspect, the present invention provides a triode FED using carbon nanotubes, which includes front and rear substrates disposed to face each other and separated by a predetermined distance, cathode lines formed on the rear substrate in a striped pattern, carbon nanotubes formed on the cathode lines at regular intervals, anode lines formed on the front substrate in a striped pattern crossing the cathode lines, phosphor formed on the anode lines, and extraction electrodes formed on the front substrate on which the anodes are formed, each extraction electrode being separated from each adjacent anode by a predetermined distance, the extraction electrodes being formed in a striped pattern parallel to the anode lines.